Robert Hahn (of the University of Oxford) and I were privileged to participate in the conference (a video of our presentation is available here). We recognized that the fiftieth anniversary of the publication of Coase’s landmark study provided an opportunity for us to examine one of that study’s key implications, which is of great importance not only for economics but for public policy as well, in particular, for environmental policy.

The Coase Theorem and the Independence Property

In our article, “The Effect of Allowance Allocations on Cap-and-Trade System Performance,” Hahn and I took as our starting point a well-known result from Coase’s work, namely, that bilateral negotiation between the generator and the recipient of an externality will lead to the same efficient outcome regardless of the initial assignment of property rights, in the absence of transaction costs, income effects, and third party impacts. This result, or a variation of it, has come to be known as the Coase Theorem.

We focused on an idea that is closely related to the Coase theorem, namely, that the market equilibrium in a cap-and-trade system will be cost-effective and independent of the initial allocation of tradable rights (typically referred to as permits or allowances). That is, the overall cost of achieving a given emission reduction will be minimized, and the final allocation of permits will be independent of the initial allocation, under certain conditions (conditional upon the permits being allocated freely, i.e., not auctioned). We called this the independence property. It is closely related to a core principle of general equilibrium theory (Arrow and Debreu 1954), namely, that when markets are complete, outcomes remain efficient even after lump-sum transfers among agents.

The Practical Political Importance of the Independence Property

We were interested in the independence property because of its great political importance. The reason why this property is of such great relevance to the practical development of public policy is that it allows equity and efficiency concerns to be separated. In particular, a government can set an overall cap of pollutant emissions (a pollution reduction goal) and leave it up to a legislature to construct a constituency in support of the program by allocating shares of the allowances to various interests, such as sectors and geographic regions, without affecting either the environmental performance of the system or its aggregate social costs. Indeed, this property is a key reason why cap-and-trade systems have been employed and have evolved as the preferred instrument in a variety of environmental policy settings.

In Theory, Does the Property Always Hold?

Because of the importance of this property, we examined the conditions under which it is more or less likely to hold — both in theory and in practice. In short, we found that in theory, a number of factors can lead to the independence property being violated. These are particular types of transaction costs in cap-and-trade markets; significant market power in the allowance market; uncertainty regarding the future price of allowances; conditional allowance allocations, such as output-based updating-allocation mechanisms; non-cost-minimizing behavior by firms; and specific kinds of regulatory treatment of participants in a cap-and-trade market.

I hope some of may find time to read our article, but a quick summary of our assessment is that we found modest support for the independence property in the seven cases we examined (but also recognized that it would surely be useful to have more empirical research in this realm).

Political Judgments

That the independence property appears to be broadly validated provides support for the efficacy of past political judgments regarding constituency building through legislatures’ allowance allocations in cap-and-trade systems. Governments have repeatedly set the overall emissions cap and then left it up to the political process to allocate the available number of allowances among sources to build support for an initiative without reducing the system’s environmental performance or driving up its cost.

This success with environmental cap-and-trade systems should be contrasted with many other public policy proposals for which the normal course of events is that the political bargaining that is necessary to develop support reduces the effectiveness of the policy or drives up its overall cost. So, the independence property of well-designed and implemented cap-and-trade systems is hardly something to be taken for granted. It is of real political importance and remarkable social value. It is just one of many lasting contributions of Ronald Coase.

Robert Stavins is the Albert Pratt Professor of Business and Government, Director, Harvard Environmental Economics Program and Chairman, Environment & Natural Resources Faculty Group at the John F. Kennedy School of Government, Harvard University